Numerous types of fluid dispensing apparatuses exist for filling bottles. One type of fluid dispensing apparatus which is in widespread use is positive displacement fillers. Positive displacement fillers typically include moving parts which contact and displace the fluid being dispensed. For example, one type of positive displacement filler uses a piston and cylinder arrangement. In this type of positive displacement filler, the backward movement of the piston draws fluid into the cylinder through an inlet port and the forward movement of the piston expels the fluid through an outlet port. Another type of positive displacement filler uses a rotary pump to move the fluid.
Positive displacement pumps have gained widespread use in the United States for two reasons. First, positive displacement pumps can operate at relatively high speeds, filling as many as six hundred bottles per minute. Additionally, positive displacement pumps are accurate up to about ±0.5%.
Despite the widespread use of positive displacement fillers, they nevertheless have several disadvantages. One disadvantage with positive displacement fillers is that the fluid comes into contact with moving parts. As the moving parts wear, particulate matter enters the fluid causing particulate contamination. If severe enough, particulate contamination can render the product unusable. Another disadvantage with positive displacement fillers involves the difficulty in cleaning and sterilizing the moving parts in contact with the fluid. In positive displacement pumps, the critical tolerances between pads, such as the piston and cylinder, precludes effective cleaning in place. Thus, the user must disassemble the apparatus for cleaning and sterilization. This process is not only time consuming, but may result in biological contamination of the pads when they are handled by the mechanic during re-assembly.
Another type of fluid dispensing apparatus is the time/pressure filler. Generally speaking, the time/pressure filler includes a fluid reservoir which is maintained under a relatively constant pressure. The fluid is dispensed from the reservoir through a compressible line. Fluid flow is shut off by a pinch type valve which squeezes and collapses the discharge line. A pre-determined volume of fluid is dispensed by opening the discharge line for a pre-determined period of time and then closing the line. If the pressure within the fluid reservoir is maintained constant, an equal amount of fluid should be dispensed each time the cycle is repeated. However, time/pressure fillers do not work as well in practice as they do in theory.
Another type of fluid dispensing apparatus is shown in U.S. Pat. No. 5,090,594 which discloses a volumetric fluid dispensing apparatus. The volumetric dispensing apparatus measures a predetermined volume of fluid in a measuring cup or fill tube which is subsequently dispensed into a receptacle. Volumetric fillers, while slower than positive displacement fillers, are highly accurate and avoid the problems of microbial and particulate contamination. However, volumetric fillers, like time/pressure fillers, depend on a relatively constant pressure. For this reason, it is impractical to use clarification filters in volumetric fillers since the pressure drop across the filter may result in inaccurate filling.
Another type of fluid dispensing apparatus is described in U.S. Pat. No. 5,480,063, issued to Keyes et al. on Jan. 2, 1996. Keyes et al. describe an apparatus having no moving parts in contact with the fluid being dispensed. The fluid-dispensing apparatus includes a fluid chamber containing the fluid to be dispensed and a fill tube communicatively connected to the fluid chamber. The fill tube forms a circuit with the fluid reservoir. In operation, fluid is transferred from the chamber into the fill tube. When the fluid level in the fill tube reaches a predetermined height, filling is terminated and fluid dispensed from the fill tube into a container. See also, U.S. Pat. No. 5,680,960, issued to Keyes et al., on Oct. 28, 1997.
Despite the approaches embodied in the aforementioned patents, there is a continuing need for improvements to and/or alternative configurations for fluid dispensing apparatuses, particularly those implementing disposable single-use, fluid handling components.